Vehicle lamp



Aug. 11, 1931. w. H. WOOD 1,818,183

VEHICLE LAMP Filed May 18, 1925 figz Reissued Aug. 11, 1931.

PATENT OFFICE WILLIAM H. WOOD, OF SOUTH EUCLID, OHIO VEHICLE LAMP Application filed May 18,

This invention relates to headlights for vehicles and has for its objects the provision of a lamp bulbwhich at the same time with affording the most satisfactory distribution 5 of light upon the road shall also illuminate different parts of the field with lights of different color as shown by experience to be most satisfactory to the vehicle operator; another and partially independent object 19 is the provision of a new mode of dimming the light when meeting other vehicles or drivin congested districts; the provision of means for dimming by extinguishing only a part of the light, which may be either of is the same color as the remaining part or of a difi'erent color, the distribution of the remaining part not being affected; the provision of new expedients for controllin the intensity and color of difierent parts the no light beam; while further objects and advantages of the invention will become apparent as the description proceeds.

In my Patent No. 1,533,360 issued April 14, 1925, I disclosed a lamp bulb having filaments confined within and defining a plane lattice located obliquely of and at one side of the axis so that when employed with a common parabolic reflector a downwardly spreading light beam was produced, with its region of maximum intensity just below the center of the reflector and such intensity gradually decreasing in a downward direction and suddenly decreasing in the upward andlateral directions. The present invention is an improvement thereon.

the drawings accompanying and forming a part of this application I have shown certain typical forms in which my invention is embodied. Fig. l is a plan view and Fig. 2 a side elevation of a single circuit bulb positioned as shown in Figure and containing a part of my improvements; Fig. 3 is a plan view and Fig. 4 a side elevation of a double circuit bulb likewise positioned as shown in Figure 5 and containing my improvements; Fig. 5 is an optical diagram taken slightly oif center showing the behavoir of my improved bulb in a reflector; Fig. 6 is a distribution diagram and Fig. 7 a color 1925. Serial No. 30,987.

diagram of thelight field as thrown upon a vertical. screen.

The bulb comprises the usual glass globe 1, having a spherical portion 2 at the front and a metal base3 at the rear, this base being preferably 0 lindrical and coaxial with the portion 2. ealed inside this globe are lead- 1ng-in wires, these being two in number in the single circuit bulb, one of the same, as 4, being grounded to the base, and the other, as 5, being connected to a contact 6 insulated therefrom. These leading-in wires are deflected, first upward away from the horizontal plane containing the axis aa, as shown at 7 (see Fig. 5) and then reversely toward said axis as indicated at 8, the corresponding parts of the two wires lying always in the same plane, and the portions 8, 8 are connected by one or more filaments of a type tobecome luminous under the influence of the 2C electric current. These filaments are preferably of fine wire made of a metal of high melting point and coiled into the form of fine helices so as to develop their radiation in a concentrated space. I have shown three of these filaments which is the preferred number, although either more or less can be used, and I have shown them as having their end portions slightly oblique relative to each other although they can take any shape from straight to a deeper V.

The first filament 10 is located so that its mid point falls substantially at the center of curvature of the portion 2 and, in use, at the focal point 7 of the reflector. It is preferably wound uniformly throughout its middle portion in the form of a fine helix, although the end portions, may, if desired, be left straight (or comparatively so) as shown at 11, in case bridging the entire distance with the concentrated coil would be undesirable. The same essential result would be secured by converging the ends of the leading-in wires, since the portions 11 which are not closely coiled emit comparatively little light. This filament 10 is preferably so designed as to become so highly heated under usual operating condition as to emit an intense whitelight.

The filament 12 which is furthest from the lampaxis is preferably so designed as to be- 100 come less highly heated under the same operating conditions and thus to emit a light having a ellowish hue.

It will understood by those skilled in the art that thevariations in filament-temperature herein described may be produced in several different ways, namely by changing the length of the wire, the d1ameter of the wire, the specific resistance of the wire, and the closeness with which the helix is wound- In general it may be stated that the temperature will be increased by any change which decreases the resistance offered by the filament, namely by increasing the diameter of the wire or by decreasing its length or specific resistance or by bringing the turns of thehelix more closely together. The close winding of the helix also operates by reason of the mutual heating effect to vary the resistance through the tem erature coefiicient. Owing to these interrelatlons it is impossible to specify in constructional terms the exact sizes, lengths, etc. of the different filaments but those skilled in the art will have no difficulty in choosing such wires and windin 's as shall produce the desired result, namely a bright white incandescence of the filament 10 and a more yellow incandescence of the filament 12.

Also the filament 12 may well be made with its end portions concentrated into fine helices and its mid portion comparatively uncoiled as shown at 13 so that the latter portion will operate at a lower temperature. This enables the desired lateral extension of the filament to produce the required width and downward deflection of the reflected beam without unduly increasing the length of the wire; and it tends to flatten the top of the light beam. The concentrated portions constitute, in effect, spaced light sources since the less tightly coiled portion 13 is comparatively dark.

When located in a headlight reflector, such as the paraboloid shown in Fig. 5, the axis M of the lamp coincides with the axis of the reflector, the mid point of the filament 10 substantially coinciding with the focal point f and the remainder of the filament lattice rising obliquely to the rear thereof. Light rays originating exactly at the focal point are reflected parallel to the axis as indicated by the dotted lines b?), but light rays originating at other points exhibit diverse behaviors depending upon their dis tances from the focal point and from the vertical plane which includes the lamp axis. Thus a ray of light 0 originating at the center of the filarnent 12 and falling on the up- 12 as indicated by the solid line d is deflected downwardly as shown (accentuated) at d which is the reason that the concentrate emitting portion at the ends of this filament are desirable. The light rays arising at the end portions of the filament 10 are less deflected owing to the fact that they are nearer the axial plane and this filament accordingly gives rise primarily to an intense, concentrated beam, elon ated laterally as shown at 15 in Fig. 6 whic is an attempt to portray a typical light pattern thrown on a vertical screen 50 feet from the lamp. 7

It is suflicient for practical purposes if filaments 10 and 12 only are employed, but additional filaments can be located there-between if desired, one such filament 16' being shown in the drawings. The filaments should 7 be sufiiciently close together to prevent any banded or mottled appearance and bending each filament into shallow V or arcuate shape further tends to prevent this.

The light beam produced by the filament 12 is substantiallythat indicated at 17 in Fig. 6, having a marked sagit'tate form with extensions to the points QQ: which in practice illuminate the sides of the road. When other filaments are employed, as 16, an intermediate field is illuminated as indicated at 18 in Fig. 6; and when one or both of the displaced filaments have a yellowish tinge as herein described the color of the light varies gradually from a substantial white at the A point to a marked yellowish at the Q points as attempted to be portrayed in Fig. 7. The points D D are substantially free from reflected light.

Also it is advantageous for dimming purposes to extinguish only this intense distance light, keeping the beam of lower intensity constant both in color and position. This serves to remove the dazzling rays from the eyes of meeting travelers without at the same time necessitating any pupillary adjustment on the part of the driver, since his own eye-accommodation is determined chiefly by the diflused yellow rays which remain unchanged. In order to effect this dimming it is necessary to employ an additional circuit as shown in Figs. 3 and 4. This is effected by using a third leading-in wire 20 to which one end of one filament, such as 10 is attached, one of the other leading-in wires, as 5, being correspondingly shortened, and having the corresponding ends of the remain ing filament or filaments attached thereto. One of the leading-in wires, preferably that one which is common to the two circuits, is grounded to the base while the others are connected to separate contacts, 21, 22, carried by the base and insulated therefrom and from each other. A suitable switch is used, such as shown at 24, whereby the filament 10 can be illuminated or extinguished without affecting the operation of the other filaments.

It will be understood that the diagrams herein given are merely suggestive and not intended to limit me to the particular form therein shown. The diiferent light fields are not sharply defined but merge into each other gradually, and the reflectlon occurring in three dimensions it is impossible to illustrate the same with accuracy although the final result is as described. It will also be understood that owing to parallax the light pattern on a level road is very different from what it is on a vertical screen, and that on a crowned road is still different. It will also be understood that I may employ the color variation without the dimming provisions, or the dimming provisions without the color variation, or either without the specific filament design, and these and many other changes in detail are intended to be embraced in and covered by my claims.

Having thus described my invention what I claim is:

1. A lamp bulb for headlight reflectors having a plurality of filaments arranged in the form of a plane lattice, certain of said filaments having the middle portion wound in a fine helix and the end portions comparatively uncoiled, and other of said filaments having the end portions Wound in a more closely coiled helix and the middle portion relatively uncoiled.

2. A lamp bulb for headlight reflectors having a plurality of filaments arranged in the form of a plane lattice, located obliquely at one side of the lamp axis, the filament which is nearest said axls having its middle portion wound in a fine helix and the filament which is furthest from the axis having its middle portion comparatively uncoiled and its end portions coiled in fine helices.

3. A lamp bulb for the pur ose described comprising a globe and a base aving a common axis, and filaments located in and defining a plane which intersects said axis obliquely, one of said filaments constituting a light source substantially intersected by said axis, and other filaments constituting laterally spaced light sources located in adjacent quadrants about said axis.

4. A lamp bulb for the purpose described having three light sources therein, one being of superior candle power and substantially intersected by the lamp axis and two being of less candle power and located at the same 7 side of a plane which includes the bulb axis and on opposite sides of a second plane which intersects said first plane perpendicularly along the line defined by said axis.

In testimony whereof I hereunto affix my signature.

WILLIAM H. WOOD. 

